Many types of hand-held cutters are known for cutting paper, cloth, vinyl or other soft materials. These cutters are useful for a variety of environments such as homes, schools, offices or factories for a variety of applications like pattern making, editing or artwork cut-and-paste. Among the hand-held cutters, there is a type which is particularly convenient, economical and therefore most commonly used. This type of hand-held cutter comprises a rigid housing with a large opening formed on one face. Inside the housing there is a provided a passageway which allows a retractable blade to move along the length of the housing. Movement of the blade is controlled by actuated movement, usually by the user's thumb, of a slidable member which connects with the blade by a hole-and-lug combination located near the end of the blade. The slidable member slidably engages with tracks on the edges of the opening such that it is allowed to move only along the length of the opening. The length of the portion of the blade protruding outside the housing is controlled by the slidable member which is set to be resisted and stopped at pre-defined intervals unless further actuated. Such positions are defined by notches or teeth located on at least one side of the opening above the tracks. Usually, the displacement between two successive notches equals the length of each blade segment which is usually graduated on the blade for easy break-away of the blunt portion of the blade.
After the sliding member is moved into a position thereby defining the length of the blade protruding from the housing, this position can be maintained by a wedging means which wedges the locking means of the sliding members to the notches on the sides of the openings.
When the cutter is not in use, the sliding member and the wedging means assembly forms a safety mechanism which is designed to prevent un-expected release of blade from the housing to prevent accidental cuts. If the blade is rusty, even very minor cuts can cause inflamation or tetanus. Every year, just in the United States alone, many paper cutter manufacturers have to deal with a large number of compensation claims made against them because of accidental cuts.
Such accidents frequently occur in places such as stationery shops or department stores, where the economical cutters are displayed in bulk without strong protective packaging so that customers can actually examine them and choose. The aforementioned safety means is not satisfactory especially after long-range transportation during which persistant vibrations may cause un-noticed unlocking of the locking assembly. Accidental cutting may also occur where curious children have access to cutters and accidentally unlock the locking assembly and actuate the sliding members thereby causing cuts. Such accidents may also happen to adults due to habitual tendency to push forward the sliding member while holding a cutter in hand. GB-2207073A discloses a safety cutter which incorporates a V-shaped spring locking member within a sliding member, such a cutter is more complicated, therefore more expensive, but would not offer actual solution to this safety problem as it would not prevent harm and damages due to persistent vibration, agitation among the non-individually packed cutters in transportation or subconscious habitual tendency of sliding member pushing by the thumb, thereby releasing blade. Further, repeated sliding of the spring on the plastic notches to which the spring also engages for locking will cause unnoticed wear of notches after repeated use and significantly hampers the engaging efficiency of the locking assembly.